Creusia stromia Creusia spinulosa Creusia verruca. PYRGOMA. PYROOMA
CANCELLATA.— L&Lch. This genus differs from the preceding with regard to its
form. Its valves, being more firmly united, give it the appearance of a subglobular
...

Creusia spinulosa might be added to this list; but the variation in the opercular
valves was so great & so hopelessly perplexing that after weeks of labour I had to
give up in despair the determination of what to rank as species & what as ...